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Versions: (draft-camarillo-xcon-bfcp) 00 01 02 03 04 05 06 RFC 4582

XCON Working Group                                          G. Camarillo
Internet-Draft                                                  Ericsson
Expires: July 1, 2005                                             J. Ott
                                                     Universitaet Bremen
                                                                K. Drage
                                                     Lucent Technologies
                                                       December 31, 2004


                The Binary Floor Control Protocol (BFCP)
                      draft-ietf-xcon-bfcp-03.txt

Status of this Memo

   This document is an Internet-Draft and is subject to all provisions
   of section 3 of RFC 3667.  By submitting this Internet-Draft, each
   author represents that any applicable patent or other IPR claims of
   which he or she is aware have been or will be disclosed, and any of
   which he or she become aware will be disclosed, in accordance with
   RFC 3668.

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   This Internet-Draft will expire on July 1, 2005.

Copyright Notice

   Copyright (C) The Internet Society (2004).

Abstract

   Floor control is a means to manage joint or exclusive access to
   shared resources in a (multiparty) conferencing environment.
   Thereby, floor control complements other functions -- such as
   conference and media session setup, conference policy manipulation,



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   and media control -- that are realized by other protocols.

   This document specifies the Binary Floor Control Protocol (BFCP).
   BFCP is used between floor participants and floor control servers,
   and between floor chairs (i.e., moderators) and floor control
   servers.

Table of Contents

   1.   Introduction . . . . . . . . . . . . . . . . . . . . . . . .   5
   2.   Terminology  . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.   Scope  . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.1  Floor Creation . . . . . . . . . . . . . . . . . . . . . .   8
     3.2  Obtaining Information to Contact a Floor Control Server  .   8
     3.3  Generating a Shared Secret . . . . . . . . . . . . . . . .   8
     3.4  Obtaining Floor-Resource Associations  . . . . . . . . . .   8
     3.5  Policy Enforcement . . . . . . . . . . . . . . . . . . . .   9
   4.   Overview of Operation  . . . . . . . . . . . . . . . . . . .   9
     4.1  Floor Participant to Floor Control Server Interface  . . .  10
     4.2  Floor Chair to Floor Control Server Interface  . . . . . .  13
   5.   Packet Format  . . . . . . . . . . . . . . . . . . . . . . .  14
     5.1  FIXED-HEADER Format  . . . . . . . . . . . . . . . . . . .  14
     5.2  Attribute Format . . . . . . . . . . . . . . . . . . . . .  15
       5.2.1  FLOOR-ID . . . . . . . . . . . . . . . . . . . . . . .  17
       5.2.2  USER-ID  . . . . . . . . . . . . . . . . . . . . . . .  17
       5.2.3  BENEFICIARY-ID . . . . . . . . . . . . . . . . . . . .  17
       5.2.4  TRANSACTION-ID . . . . . . . . . . . . . . . . . . . .  18
       5.2.5  FLOOR-REQUEST-ID . . . . . . . . . . . . . . . . . . .  18
       5.2.6  HUMAN-READABLE-INFO  . . . . . . . . . . . . . . . . .  18
       5.2.7  DIGEST . . . . . . . . . . . . . . . . . . . . . . . .  19
       5.2.8  REQUEST-STATUS . . . . . . . . . . . . . . . . . . . .  20
       5.2.9  ERROR-CODE . . . . . . . . . . . . . . . . . . . . . .  21
       5.2.10   USER-DISPLAY-NAME  . . . . . . . . . . . . . . . . .  23
       5.2.11   USER-URI . . . . . . . . . . . . . . . . . . . . . .  23
       5.2.12   PRIORITY . . . . . . . . . . . . . . . . . . . . . .  23
       5.2.13   NONCE  . . . . . . . . . . . . . . . . . . . . . . .  23
       5.2.14   SUPPORTED-TLVS . . . . . . . . . . . . . . . . . . .  24
     5.3  Message Format . . . . . . . . . . . . . . . . . . . . . .  24
       5.3.1  FloorRequest . . . . . . . . . . . . . . . . . . . . .  24
       5.3.2  FloorRelease . . . . . . . . . . . . . . . . . . . . .  25
       5.3.3  FloorRequestInfoWanted . . . . . . . . . . . . . . . .  25
       5.3.4  FloorRequestInfo . . . . . . . . . . . . . . . . . . .  26
       5.3.5  FloorInfoWanted  . . . . . . . . . . . . . . . . . . .  26
       5.3.6  FloorInfo  . . . . . . . . . . . . . . . . . . . . . .  27
       5.3.7  ChairAction  . . . . . . . . . . . . . . . . . . . . .  27
       5.3.8  ChairActionAck . . . . . . . . . . . . . . . . . . . .  28
       5.3.9  Hello  . . . . . . . . . . . . . . . . . . . . . . . .  28
       5.3.10   HelloAck . . . . . . . . . . . . . . . . . . . . . .  28



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       5.3.11   Error  . . . . . . . . . . . . . . . . . . . . . . .  29
   6.   Transport  . . . . . . . . . . . . . . . . . . . . . . . . .  29
   7.   Lower-Layer Security . . . . . . . . . . . . . . . . . . . .  30
   8.   Protocol Transactions  . . . . . . . . . . . . . . . . . . .  30
     8.1  Client Behavior  . . . . . . . . . . . . . . . . . . . . .  31
     8.2  Server Behavior  . . . . . . . . . . . . . . . . . . . . .  31
   9.   Authentication and Authorization . . . . . . . . . . . . . .  31
     9.1  Client Behavior  . . . . . . . . . . . . . . . . . . . . .  31
     9.2  Floor Control Server Behavior  . . . . . . . . . . . . . .  32
   10.  Floor Participant Operations . . . . . . . . . . . . . . . .  33
     10.1   Requesting a Floor . . . . . . . . . . . . . . . . . . .  33
       10.1.1   Sending a FloorRequest Message . . . . . . . . . . .  33
       10.1.2   Receiving a Response . . . . . . . . . . . . . . . .  34
     10.2   Cancelling a Floor Request and Releasing a Floor . . . .  35
       10.2.1   Sending a FloorRelease Message . . . . . . . . . . .  35
       10.2.2   Receiving a Response . . . . . . . . . . . . . . . .  36
   11.  Chair Operations . . . . . . . . . . . . . . . . . . . . . .  36
     11.1   Sending a ChairAction Message  . . . . . . . . . . . . .  36
     11.2   Receiving a Response . . . . . . . . . . . . . . . . . .  37
   12.  General Client Operations  . . . . . . . . . . . . . . . . .  38
     12.1   Requesting Information about Floors  . . . . . . . . . .  38
       12.1.1   Sending a FloorInfoWanted Message  . . . . . . . . .  38
       12.1.2   Receiving a Response . . . . . . . . . . . . . . . .  38
     12.2   Requesting Information about Floor Requests  . . . . . .  39
       12.2.1   Sending a FloorRequestInfoWanted Message . . . . . .  40
       12.2.2   Receiving a Response . . . . . . . . . . . . . . . .  40
     12.3   Obtaining the Capabilities of a Floor Control Server . .  41
       12.3.1   Sending a Hello Message  . . . . . . . . . . . . . .  41
       12.3.2   Receiving Responses  . . . . . . . . . . . . . . . .  41
   13.  Floor Control Server Operations  . . . . . . . . . . . . . .  41
     13.1   Reception of a FloorRequest Message  . . . . . . . . . .  42
       13.1.1   Generating the First FloorRequestInfo Message  . . .  42
       13.1.2   Generation of Subsequent FloorRequestInfo Messages .  43
     13.2   Reception of a FloorRequestInfoWanted Message  . . . . .  44
       13.2.1   Information on a Single Floor Request  . . . . . . .  44
       13.2.2   Information on the Floor Requests Associated to a
                Participant  . . . . . . . . . . . . . . . . . . . .  45
     13.3   Reception of a FloorRelease Message  . . . . . . . . . .  45
     13.4   Reception of a FloorInfoWanted Message . . . . . . . . .  46
       13.4.1   Generation of the First FloorInfo Message  . . . . .  47
       13.4.2   Generation of Subsequent  FloorInfo Messages . . . .  47
     13.5   Reception of a ChairAction Message . . . . . . . . . . .  48
     13.6   Reception of a Hello Message . . . . . . . . . . . . . .  49
     13.7   Error Message Generation . . . . . . . . . . . . . . . .  49
   14.  Security Considerations  . . . . . . . . . . . . . . . . . .  49
   15.  IANA Considerations  . . . . . . . . . . . . . . . . . . . .  51
     15.1   Attribute Subregistry  . . . . . . . . . . . . . . . . .  51
     15.2   Primitive Subregistry  . . . . . . . . . . . . . . . . .  51



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     15.3   Request Status Subregistry . . . . . . . . . . . . . . .  52
     15.4   Error Code Subregistry . . . . . . . . . . . . . . . . .  53
   16.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . .  54
   17.  References . . . . . . . . . . . . . . . . . . . . . . . . .  54
   17.1   Normative References . . . . . . . . . . . . . . . . . . .  54
   17.2   Informational References . . . . . . . . . . . . . . . . .  55
        Authors' Addresses . . . . . . . . . . . . . . . . . . . . .  56
        Intellectual Property and Copyright Statements . . . . . . .  57











































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1.  Introduction

   Within a conference, some applications need to manage the access to a
   set of shared resources, such as the right to send media over a
   particular media stream.  Floor control enables such applications to
   provide users with coordinated (shared or exclusive) access to these
   resources.

   The Requirements for Floor Control Protocol [11] list a set of
   requirements that need to be met by floor control protocols.  The
   Binary Floor Control Protocol (BFCP), which is specified in this
   document, meets these requirements.

   In addition, BFCP has been designed so that it can be used in
   low-bandwidth environments.  The binary encoding used by BFCP
   achieves a small message size (when message signatures are not used)
   that keeps the time it takes to transmit delay-sensitive BFCP
   messages at minimum.  Delay-sensitive BFCP messages include
   FloorRequest, FloorRelease, FloorRequestInfo, and ChairAction.  It is
   expected that future extensions to these messages do not increase the
   size of these messages in a significant way.

   The remainder of this document is organized as follows.  Section 2
   defines the terminology used throughout this document and Section 3
   discusses the scope of BFCP (i.e., which tasks fall within the scope
   of BFCP and which ones are performed using different mechanisms).
   Section 4 provides a non-normative overview of BFCP operation and
   subsequent sections provide the normative specification of BFCP.

2.  Terminology

   In this document, the key words "MUST", "MUST NOT", "REQUIRED",
   "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT
   RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as
   described in BCP 14, RFC 2119 [2] and indicate requirement levels for
   compliant implementations.

   Media Participant: An entity that has access to the media resources
   of a conference (e.g., it can receive a media stream).  In
   floor-controlled conferences, a given media participant is typically
   co-located with a floor participant, but does not need to.
   Third-party floor requests consist of having a floor participant
   request a floor for a media participant when they are not colocated.
   The protocol between a floor participant and a media participant
   (that are not colocated) is outside the scope of this document.

   Client: a floor participant or a floor chair that communicate with a
   floor control server using BFCP.



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   Conference Policy: The complete set of rules for a particular
   conference.  It includes the membership policy, the media policy, and
   policies related to floors and the use of floor control protocols.
   There is an instance of conference policy for each conference.

   Floor: A permission to temporarily access or manipulate a specific
   shared resource or set of resources.

   Floor Chair: A logical entity that manages one floor (grants, denies,
   or revokes a floor).  An entity that assumes the logical role of a
   floor chair for a given transaction may assume a different role
   (e.g., floor participant) for a different transaction.  The roles of
   floor chair and floor participant are defined on a
   transaction-by-transaction basis.  BFCP transactions are defined in
   Section 8.

   Floor Control: A mechanism that enables applications or users to gain
   safe and mutually exclusive or non-exclusive input access to the
   shared object or resource.

   Floor Control Server: A logical entity that maintains the state of
   the floor(s) including which floors exists, who the floor chairs are,
   who holds a floor, etc.  Requests to manipulate a floor are directed
   at the floor control server.  The floor control server of a
   conference may perform other logical roles (e.g., floor participant)
   in another conference.

   Floor Participant: A logical entity that requests floors, and
   possibly information about them, from a floor control server.  An
   entity that assumes the logical role of a floor participant for a
   given transaction may assume a different role (e.g., a floor chair)
   for a different transaction.  The roles of floor participant and
   floor chair are defined on a transaction-by-transaction basis.  BFCP
   transactions are defined in Section 8.  In floor-controlled
   conferences, a given floor participant is typically co-located with a
   media participant, but does not need to.  Third-party floor requests
   consist of having a floor participant request a floor for a media
   participant when they are not co-located.

   Participant: An entity that acts as a floor participant, as a media
   participant, or as both.

3.  Scope

   As stated earlier, BFCP is a protocol to coordinate access to shared
   resources in a conference following the requirements defined in [11].
   Floor control complements other functions defined in the conferencing
   framework [12].  In particular, it is the conference policy that



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   defines which media streams and applications are floor-controlled,
   who is/are the respective floor chair(s), and how access to the floor
   is managed.  Furthermore, it is up to the media policy to define
   which (if any) impact on media stream handling (e.g.  switching or
   mixing) assignment of a floor to a media participant has.

   The floor control protocol BFCP defined in this document only
   specifies a means to arbitrate access to floors.  The rules and
   constraints for floor arbitration and the results of floor
   assignments are outside the scope of this document and defined by
   other protocols [13].

   Figure 1 shows the tasks that BFCP can perform.


                              +---------+
                              |  Floor  |
                              |  Chair  |
                              |         |
                              +---------+
                                 ^   |
                                 |   |
                    Notification |   | Decision
                                 |   |
                                 |   |
                      Floor      |   v
   +-------------+   Request  +---------+              +-------------+
   |    Floor    |----------->|  Floor  | Notification |    Floor    |
   | Participant |            | Control |------------->| Participant |
   |             |<-----------|  Server |              |             |
   +-------------+ Granted or +---------+              +-------------+
                     Denied

                Figure 1: Functionality provided by BFCP

   BFCP provides a means:

   o  for floor participants to send floor requests to floor control
      servers.
   o  for floor control servers to grant or deny requests to access a
      given resource from floor participants.
   o  for floor chairs to send floor control servers decisions regarding
      floor requests.
   o  for floor control servers to keep floor participants and floor
      chairs informed about the status of a given floor or a given floor
      request.

   Even though tasks that do not belong to the previous list are outside



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   the scope of BFCP, some of these out-of-scope tasks relate to floor
   control and are essential to create floors and to establish BFCP
   connections between different entities.  In the following
   subsections, we discuss some of these tasks and mechanisms to perform
   them.

3.1  Floor Creation

   The association of a given floor with a resource or a set of
   resources (e.g., media streams) is out of the scope of BFCP as
   described in [13].  The conference policy for a particular conference
   contains the floors of the conference and the resource or resources
   associated with each floor.  For example, a conference may have two
   floors: one controlling who can talk at a particular time and another
   controlling who can write on a shared whiteboard.

   Floor creation and termination are also outside the scope of BFCP and
   are aspects of the conference policy as well.  Consequently, the
   floor control server needs to stay up to date on changes on the
   conference policy (e.g., when a new floor is created).

3.2  Obtaining Information to Contact a Floor Control Server

   A client needs a set of data in order to establish a BFCP connection
   to a floor control server.  These data include the transport address
   of the server, the conference identifier, and the user identifier.

   Clients can obtain this information in different ways.  One is to use
   an offer/answer [10] exchange.  How to use an SDP [8] offer/answer
   [10] exchange to obtain this information is described in [14].

3.3  Generating a Shared Secret

   Authentication in BFCP is based on a shared secret between the client
   and the floor control server.  So, there is a need for a mechanism to
   generate such a shared secret.  However, such mechanism is outside
   the scope of BFCP.

   Shared secrets can also be generated and exchanged using out-of-band
   means.  For example, when the floor participant or the floor chair
   obtains the information needed to contact the BFCP floor control
   server over a secure channel (e.g., an offer/answer [10] exchange
   using SIP [9] protected using S/MIME), they can get the shared secret
   using the same channel.

3.4  Obtaining Floor-Resource Associations

   Floors are associated with resources.  For example, a floor that



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   controls who talks at a given time has a particular audio stream as
   its associated resource.  Associations between floors and resources
   are part of the conference policy.

   Floor participants and floor chairs need to know which resources are
   associated with which floors.  They can obtain this information using
   different mechanisms, such as an offer/answer [10] exchange.  How to
   use an offer/answer exchange to obtain these associations is
   described in [14].

      Note that floor participants perform offer/answer exchanges with
      the SIP focus of the conference.  So, the SIP focus needs to
      obtain information about associations between floors and resources
      in order to be able to provide this information to a floor
      participant in an offer/answer exchange.

3.5  Policy Enforcement

   A participant whose floor request is granted has the right to use (in
   a certain way) the resource or resources associated with the floor
   that was requested.  For example, the participant may have the right
   to send media over a particular audio stream.

   Nevertheless, holding a floor does not imply that others will not be
   able to use its associated resources at the same time, even if they
   do not have the right to do so.  According to the definition in
   Section 2, the conference policy determines which media participants
   can actually use the resources in the conference.

   So, if the policy of a conference is to enforce floor control
   decisions, every change in the status of any floor needs to be
   reflected in the conference policy of the conference.  For example,
   the mixer only accepts media from the user who holds the floor.

4.  Overview of Operation

   This section provides a non-normative description of BFCP operations.
   Section 4.1 describes the interface between floor participants and
   floor control servers and Section 4.2 describes the interface between
   floor chairs and floor control servers

   BFCP messages, which use a TLV (Type-Length-Value) binary encoding,
   consist of a common header followed by a set of TLVs.  The common
   header contains, among other information, a 32-bit conference
   identifier.  Floor participants, media participants, and floor chairs
   are identified by a 16-bit user identifier, which is carried in a
   TLV.




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   There are two types of transactions in BFCP: client-initiated
   transactions and server-initiated transactions.  Client-initiated
   transactions consist of a message from a client to the floor control
   server and a response from the floor control server to the client.
   Both messages can be related because they carry the same
   TRANSACTION-ID TLV.  Server-initiated transactions consist of a
   single message, which has no TRANSACTION-ID TLV, from the floor
   control server to a client.

4.1  Floor Participant to Floor Control Server Interface

   Floor participants request a floor by sending a FloorRequest message
   to the floor control server.  BFCP supports third-party floor
   requests.  That is, the floor participant sending the floor request
   need not be co-located with the media participant that will get the
   floor once the floor request is granted.  FloorRequest messages carry
   the identity of the requester in a USER-ID TLV, and the identity of
   the beneficiary of the floor, in third party floor requests, in a
   BENEFICIARY-ID TLV.

      Third party floor requests can be sent, for example, by floor
      participants that have a BFCP connection to the floor control
      server but that are not media participants (i.e., they do not
      handle any media).

   FloorRequest messages identify the floor or floors being requested by
   carrying their 16-bit floor identifiers in FLOOR-ID TLVs.  If a
   FloorRequest message carries more than one floor identifier, the
   floor control server treats all the floor requests as an atomic
   package.  That is, the floor control server either grants or denies
   all the floors in the FloorRequest message.

   Floor control servers respond to FloorRequest messages with
   FloorRequestInfo messages, which provide information about the status
   of the floor request.  The first FloorRequestInfo message is the
   response to the FloorRequest message from the client, and therefore
   carries the same TRANSACTION-ID TLV as the FloorRequest.

   Additionally, the first FloorRequestInfo message carries a
   FLOOR-REQUEST-ID TLV.  Subsequent FloorRequestInfo messages related
   to the same floor request will carry the same FLOOR-REQUEST-ID TLV.
   This way, the floor participant can associate them with the
   appropriate floor request.

   Messages from the floor participant related to a particular floor
   request also use the same FLOOR-REQUEST-ID TLV as the first
   FloorRequestInfo Message from the floor control server.




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   Figure 2 shows how a floor participant requests a floor, obtains it,
   and, at a later time, releases it.  This figure illustrates the use,
   among other TLVs, of the TRANSACTION-ID and the FLOOR-REQUEST-ID
   TLVs.



     Floor Participant                                 Floor Control
                                                          Server
             |(1) FloorRequest                               |
             |TRANSACTION-ID: 123                            |
             |USER-ID: 234                                   |
             |FLOOR-ID: 543                                  |
             |---------------------------------------------->|
             |(2) FloorRequestInfo                           |
             |TRANSACTION-ID: 123                            |
             |USER-ID: 234                                   |
             |FLOOR-REQUEST-ID: 789                          |
             |FLOOR-ID: 543                                  |
             |REQUEST-STATUS: Pending                        |
             |<----------------------------------------------|
             |(3) FloorRequestInfo                           |
             |USER-ID: 234                                   |
             |FLOOR-REQUEST-ID: 789                          |
             |FLOOR-ID: 543                                  |
             |REQUEST-STATUS: Accepted (1st in Queue)        |
             |<----------------------------------------------|
             |(4) FloorRequestInfo                           |
             |USER-ID: 234                                   |
             |FLOOR-REQUEST-ID: 789                          |
             |FLOOR-ID: 543                                  |
             |REQUEST-STATUS: Granted                        |
             |<----------------------------------------------|
             |(5) FloorRelease                               |
             |TRANSACTION-ID: 154                            |
             |USER-ID: 234                                   |
             |FLOOR-REQUEST-ID: 789                          |
             |---------------------------------------------->|
             |(6) FloorRequestInfo                           |
             |TRANSACTION-ID: 154                            |
             |USER-ID: 234                                   |
             |FLOOR-REQUEST-ID: 789                          |
             |FLOOR-ID: 543                                  |
             |REQUEST-STATUS: Released                       |
             |<----------------------------------------------|


               Figure 2: Requesting and releasing a floor



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   Figure 2 shows how a floor participant requests to be informed on the
   status of a floor.  The first FloorInfo message from the floor
   control server is the response to the FloorInfoWanted message, and as
   such, carries the same TRANSACTION-ID TLV as the FloorInfoWanted
   message.

   Subsequent FloorInfo messages consist of server-initiated
   transactions, and therefore carry no TRANSACTION-ID TLV.  FloorInfo
   message (2) indicates that there are currently two floor requests for
   the floor whose Floor ID is 543.  FloorInfo message (3) indicates
   that the floor requests with Floor Request ID 764 has been granted,
   while the floor request with Floor Request ID 635 is the first in the
   queue.  FloorInfo message (4) indicates that the floor request with
   Floor Request ID 635 has been granted.



     Floor Participant                                 Floor Control
                                                          Server
             |(1) FloorInfoWanted                            |
             |TRANSACTION-ID: 257                            |
             |USER-ID: 234                                   |
             |FLOOR-ID: 543                                  |
             |---------------------------------------------->|
             |(2) FloorInfo                                  |
             |TRANSACTION-ID: 257                            |
             |USER-ID: 234                                   |
             |FLOOR-ID:543                                   |
             |FLOOR-REQUEST-ID: 764                          |
             |FLOOR-ID: 543                                  |
             |BENEFICIARY-ID: 124                            |
             |REQUEST-STATUS: Accepted (1st in Queue)        |
             |FLOOR-REQUEST-ID: 635                          |
             |BENEFICIARY-ID: 154                            |
             |FLOOR-ID: 543                                  |
             |REQUEST-STATUS: Accepted (2nd in Queue)        |
             |<----------------------------------------------|
             |(3) FloorInfo                                  |
             |USER-ID: 234                                   |
             |FLOOR-ID:543                                   |
             |FLOOR-REQUEST-ID: 764                          |
             |FLOOR-ID: 543                                  |
             |BENEFICIARY-ID: 124                            |
             |REQUEST-STATUS: Granted                        |
             |FLOOR-REQUEST-ID: 635                          |
             |BENEFICIARY-ID: 154                            |
             |FLOOR-ID: 543                                  |
             |REQUEST-STATUS: Accepted (1st in Queue)        |



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             |<----------------------------------------------|
             |(4) FloorInfo                                  |
             |USER-ID: 234                                   |
             |FLOOR-ID:543                                   |
             |FLOOR-REQUEST-ID: 635                          |
             |BENEFICIARY-ID: 154                            |
             |FLOOR-ID: 543                                  |
             |REQUEST-STATUS: Granted                        |
             |<----------------------------------------------|


          Figure 3: Obtaining status information about a floor

   FloorInfo messages contain information about the floor requests they
   carry.  For example, FloorInfo message (4) indicates that the floor
   request with Floor Request ID 635 has as the beneficiary (i.e., the
   participant that holds the floor when a particular floor request is
   granted) the participant whose User ID is 154.  The floor request
   applies only to the floor whose Floor ID is 543.  That is, this is
   not a multi-floor floor request.

4.2  Floor Chair to Floor Control Server Interface

   Figure 4 shows a floor chair instructing a floor control server to
   grant a floor.  Note, however, that although the floor control server
   needs to take into consideration the instructions received in
   ChairAction messages (e.g., granting a floor), it does not
   necessarily need to perform them exactly as requested by the floor
   chair.  The operation that the floor control server performs depends
   on the ChairAction message and on the internal state of the floor
   control server.

   For example, a floor chair may send a ChairAction message granting a
   floor which was requested as part of an atomic floor request
   operation that involved several floors.  Even if the chair
   responsible for one of the floors instructs the floor control server
   to grant the floor, the floor control server will not grant it until
   the chairs responsible for the other floors agree to grant them as
   well.  In another example, a floor chair may instruct the floor
   control server to grant a floor to a participant.  The floor control
   server needs to revoke the floor from its current holder before
   granting it to the new participant.

   So, the floor control server is ultimately responsible to keep a
   coherent floor state using instructions from floor chairs as input to
   this state.





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        Floor Chair                                    Floor Control
                                                          Server
             |(1) ChairAction                                |
             |TRANSACTION-ID: 769                            |
             |USER-ID: 357                                   |
             |FLOOR-ID: 543                                  |
             |FLOOR-REQUEST-ID: 635                          |
             |REQUEST-STATUS: Granted                        |
             |---------------------------------------------->|
             |(2) ChairActionAck                             |
             |TRANSACTION-ID: 769                            |
             |USER-ID: 357                                   |
             |<----------------------------------------------|


          Figure 4: Chair instructing the floor control server


5.  Packet Format

   BFCP packets consist of an 8-byte fixed header followed by
   attributes.  All the protocol values MUST be sent in network byte
   order.

5.1  FIXED-HEADER Format

   The following is the FIXED-HEADER format.


      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Ver |Reserved |  Primitive    |        Payload Length         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                         Conference ID                         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 5: FIXED-HEADER format

   Ver: the 3-bit version field MUST be set to 1 to indicate this
   version of BFCP.

   Reserved: at this point, the 5 bits in the reserved field SHOULD be
   set to zero by the sender of the message and MUST be ignored by the
   receiver.

   Primitive: this 8-bit field identifies the main purpose of the
   message.  The following primitive values are defined:



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       +-------+------------------------+-----------------------+
       | Value | Primitive              | Direction             |
       +-------+------------------------+-----------------------+
       |   0   | FloorRequest           | P -> S                |
       |   1   | FloorRelease           | P -> S                |
       |   2   | FloorRequestInfoWanted | P -> S ; Ch -> S      |
       |   3   | FloorRequestInfo       | P <- S ; Ch <- S      |
       |   4   | FloorInfoWanted        | P -> S ; Ch -> S      |
       |   5   | FloorInfo              | P <- S ; Ch <- S      |
       |   6   | ChairAction            | Ch -> S               |
       |   7   | ChairActionAck         | Ch <- S               |
       |   8   | Hello                  | P -> S ; Ch -> S      |
       |   9   | HelloAck               | P <- S ; Ch <- S      |
       |   10  | Error                  | P <- S ; Ch <- S      |
       +-------+------------------------+-----------------------+


         S:  Floor Control Server
         P:  Floor Participant
         Ch: Floor Chair

                        Table 1: BFCP primitives

   Payload Length: this 16-bit field contains length of the message in
   4-byte units excluding the fixed header.

   Conference ID: this 32-bit identifies the conference the message
   belongs to.

5.2  Attribute Format

   BFCP attributes are encoded in TLV (Type-Length-Value) format.  TLVs
   are 32-bit aligned.


















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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |    Type     |M|    Length     |                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
     |                                                               |
     /                       Attribute Contents                      /
     /                                                               /
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                          Figure 6: TLV format

   Type: this 7-bit field contains the type of the attribute.  The
   following attribute types are defined:

                     +------+---------------------+
                     | Type | Attribute           |
                     +------+---------------------+
                     |   0  | FLOOR-ID            |
                     |   1  | USER-ID             |
                     |   2  | BENEFICIARY-ID      |
                     |   3  | TRANSACTION-ID      |
                     |   4  | FLOOR-REQUEST-ID    |
                     |   5  | HUMAN-READABLE-INFO |
                     |   6  | DIGEST              |
                     |   7  | REQUEST-STATUS      |
                     |   8  | ERROR-CODE          |
                     |   9  | USER-DISPLAY-NAME   |
                     |  10  | USER-URI            |
                     |  11  | PRIORITY            |
                     |  12  | NONCE               |
                     |  13  | SUPPORTED-TLVS      |
                     +------+---------------------+

                        Table 2: BFCP attributes

   M: the 'M' bit, known as the Mandatory bit, indicates whether support
   of the attribute is required.  If an unrecognized attribute with the
   'M' bit set is received, the message is rejected.

   Length: this 8-bit field contains the length of the attribute in
   bytes, excluding any padding defined for specific attributes.  The
   Type, 'M' bit, and Length fields are included.

   Attribute Contents: the contents of the different TLVs are defined in
   the following sections.




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5.2.1  FLOOR-ID

   The following is the format of the FLOOR-ID attribute.


      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 0 0 0|M|0 0 0 0 0 1 0 0|           Floor ID            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 7: FLOOR-ID format

   Floor ID: this field contains a 16-bit value that uniquely identifies
   a floor within a conference.

5.2.2  USER-ID

   The following is the format of the USER-ID attribute.


      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 0 0 1|M|0 0 0 0 0 1 0 0|            User ID            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                        Figure 8: USER-ID format

   User ID: this field contains a 16-bit value that uniquely identifies
   a user within a conference.

5.2.3  BENEFICIARY-ID

   The following is the format of the BENEFICIARY-ID attribute.


      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 0 1 0|M|0 0 0 0 0 1 0 0|        Beneficiary ID         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 9: BENEFICIARY-ID format

   Beneficiary ID: this field contains a 16-bit value that uniquely
   identifies a user within a conference.




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5.2.4  TRANSACTION-ID

   The following is the format of the TRANSACTION-ID attribute.


      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 0 1 1|M|0 0 0 0 0 1 0 0|        Transaction ID         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 10: TRANSACTION-ID format

   Transaction ID: this field contains a 16-bit value that allows users
   to match a given message with its response.

5.2.5  FLOOR-REQUEST-ID

   The following is the format of the FLOOR-REQUEST-ID attribute.


      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 1 0 0|M|0 0 0 0 0 1 0 0|       Floor Request ID        |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 11: FLOOR-REQUEST-ID format

   Floor Request ID: this field contains a 16-bit value that indentifies
   a floor request at the floor control server.

5.2.6  HUMAN-READABLE-INFO

   The following is the format of the HUMAN-READABLE-INFO attribute.
















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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 1 0 1|M|    Length     |                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
     |                                                               |
     /                             Text                              /
     /                                               +-+-+-+-+-+-+-+-+
     |                                               |    Padding    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Figure 12: HUMAN-READABLE-INFO format

   Text: this field contains UTF-8 [7] encoded text.

   In some situations, the contents of the Text field may be generated
   by an automaton.  If such automaton has information about the
   preferred language of the receiver of a particular
   HUMAN-READABLE-INFO TLV, it MAY use this language to generate the
   Text field.

   Padding: one, two, or three bytes of padding added so that the
   contents of the HUMAN-READABLE-INFO TLV is 32-bit aligned.  The
   Padding bits SHOULD be set to zero by the sender and MUST be ignored
   by the receiver.  If the TLV is already 32-bit aligned, no padding is
   needed.

5.2.7  DIGEST

   The following is the format of the DIGEST attribute.





















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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 1 1 0|M|0 0 0 1 1 0 0 0|                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
     |                                                               |
     +                                                               +
     |                                                               |
     +                          HMAC-SHA1                            +
     |                                                               |
     +                                                               +
     |                                                               |
     +                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                               |             Padding           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                        Figure 13: DIGEST format

   HMAC-SHA1: this 20-byte field contains an HMAC-SHA1 [1] of the BFCP
   message.  Its calculation is described in Section 9.

   Padding: two bytes of padding added so that the contents of the
   HMAC-SHA1 TLV is 32-bit aligned.  The Padding bits SHOULD be set to
   zero by the sender and MUST be ignored by the receiver.

5.2.8  REQUEST-STATUS

   The following is the format of the REQUEST-STATUS attribute.


      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 0 1 1 1|M|0 0 0 0 0 1 0 0|Request Status |Queue Position |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 14: REQUEST-STATUS format

   Request Status: this 8-bit field contains the status of the request,
   as described in the following table.










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                         +-------+-----------+
                         | Value | Status    |
                         +-------+-----------+
                         |   0   | Pending   |
                         |   1   | Accepted  |
                         |   2   | Granted   |
                         |   3   | Denied    |
                         |   4   | Cancelled |
                         |   5   | Released  |
                         |   6   | Revoked   |
                         +-------+-----------+

                     Table 3: Request Status values

   Queue Position: this 8-bit field contains, when applicable, the
   position of the floor request in the floor request queue at the
   server.  If the Request Status value is different from Accepted, the
   floor control server does not implement a floor request queue, or the
   floor control server does not want to provide the client with this
   information, all the bits of this field SHOULD be set to zero.

   A floor request is in Pending state if the floor control server needs
   to contact a floor chair in order to accept the floor request, but
   has not done it yet.  Once the floor control chair accepts the floor
   request, the floor request is moved to the Accepted state.

5.2.9  ERROR-CODE

   The following is the format of the ERROR-CODE attribute.


      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 1 0 0 0|M|    Length     |          Error Code           |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     |                     Error Specific Details                    |
     /                                                               /
     /                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                               |            Padding            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 15: ERROR-CODE format

   Error Code: this 16-bit field contains an error code from the
   following table.




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   +---------------------------------+---------------------------------+
   |              Value              | Meaning                         |
   +---------------------------------+---------------------------------+
   |                0                | Conference does not Exist       |
   |                1                | Authentication Failed           |
   |                2                | Unknown Mandatory TLV           |
   |                3                | Floor Request ID Does Not Exist |
   |                4                | Unauthorized Operation          |
   |                5                | User does not Exist             |
   |                6                | Invalid Nonce                   |
   |                7                | DIGEST TLV Required             |
   |                8                | Invalid Floor ID                |
   |                9                | You have Already Reached the    |
   |                                 | Maximum Number of Ongoing Floor |
   |                                 | Requests for this Floor         |
   +---------------------------------+---------------------------------+

                      Table 4: Error Code meaning

   Error Specific Details: Present only for certain Error Codes.  In
   this document, only for Error Code 2 (Unknown Mandatory TLV).  For
   Error Code 2, this field contains the Types of the TLVs (which were
   present in the message that triggered the Error message) that were
   unknown to the receiver, encoded as follows.


      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      Unknown TLV Type         |      Unknown TLV Type         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     /                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                               |      Unknown TLV Type         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      Unknown TLV Type         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 16: Unknown TLVs format

   Padding: one, two, or three bytes of padding added so that the
   contents of the ERROR-CODE TLV is 32-bit aligned.  If the TLV is
   already 32-bit aligned, no padding is needed.

   The Padding bits SHOULD be set to zero by the sender and MUST be
   ignored by the receiver.  Note all the Error Codes defined in this
   document but Error Code 2, result in a TLV which is already 32-bit
   aligned (i.e., no need of padding).  Error Code 2 results in a TLV



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   that may need 2 bytes of padding.

5.2.10  USER-DISPLAY-NAME

   The format of the USER-DISPLAY-NAME attribute is the same as the
   HUMAN-READABLE-INFO attribute (still, they have different attribute
   types).  The Text field in the USER-DISPLAY-NAME attribute contains
   the name of the user.

5.2.11  USER-URI

   The format of the USER-URI attribute is the same as the
   HUMAN-READABLE-INFO attribute (still, they have different attribute
   types).  The Text field in the USER-URI attribute contains the URI of
   the user.

5.2.12  PRIORITY

   The following is the format of the PRIORITY attribute.


      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 1 0 1 1|M|0 0 0 0 0 1 0 0|   Priority    |   Reserved    |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Figure 17: PRIORITY format

   Priority: the higher the 8-bit value, the more priority is requested
   for a given floor request.

   Reserved: at this point, the 8 bits in the reserved field SHOULD be
   set to zero by the sender of the message and MUST be ignored by the
   receiver.

5.2.13  NONCE

   The following is the format of the NONCE attribute.












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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 1 1 0 0|M|    Length     |          Nonce Value          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                        Figure 18: NONCE format

   Nonce Value: this 16-bit field contains a nonce.

5.2.14  SUPPORTED-TLVS

   The following is the format of the SUPPORTED-TLVS attribute.


      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 1 1 0 1|M|    Length     |         Supported TLV         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Supported TLV         |         Supported TLV         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     /                                                               /
     /                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                               |            Padding            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 19: SUPPORTED-TLVS format

   Supported TLV: these fields contain the Types of the TLVs that are
   supported by the floor control server.

   Padding: two bytes of padding added so that the contents of the
   SUPPORTED-TLVS TLV is 32-bit aligned.  If the TLV is already 32-bit
   aligned, no padding is needed.

   The Padding bits SHOULD be set to zero by the sender and MUST be
   ignored by the receiver.

5.3  Message Format

   This section contains the normative ABNF [3] of the BFCP messages.

5.3.1  FloorRequest

   Floor participants request a floor by sending a FloorRequest message
   to the floor control server.  The following is the format of the



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   FloorRequest message:


   FloorRequest =   (FIXED-HEADER)
                    (TRANSACTION-ID)
                    (USER-ID)
                    [BENEFICIARY-ID]
                   *(FLOOR-ID)
                    [HUMAN-READABLE-INFO]
                    [PRIORITY]
                    [NONCE]
                    [DIGEST]

                     Figure 20: FloorRequest format


5.3.2  FloorRelease

   Floor participants release a floor by sending a FloorRelease message
   to the floor control server.  Floor participants also use the
   FloorRelease message to cancel pending floor requests.  The following
   is the format of the FloorRelease message:


   FloorRelease =   (FIXED-HEADER)
                    (TRANSACTION-ID)
                    (USER-ID)
                    (FLOOR-REQUEST-ID)
                    [NONCE]
                    [DIGEST]

                     Figure 21: FloorRelease format


5.3.3  FloorRequestInfoWanted

   Floor participants and floor chairs request information about a floor
   request by sending a FloorRequestInfoWanted message to the floor
   control server.  The following is the format of the
   FloorRequestInfoWanted message:











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   FloorRequestInfoWanted =   (FIXED-HEADER)
                              (TRANSACTION-ID)
                              (USER-ID)
                              [BENEFICIARY-ID]
                              [FLOOR-REQUEST-ID]
                              [NONCE]
                              [DIGEST]

                Figure 22: FloorRequestInfoWanted format


5.3.4  FloorRequestInfo

   The floor control server informs floor participants and floor chairs
   about the status of their floor requests by sending them
   FloorRequestInfo messages.  The following is the format of the
   FloorRequestInfo message:


   FloorRequestInfo =     (FIXED-HEADER)
                          (TRANSACTION-ID)
                          (USER-ID)
                          [BENEFICIARY-ID]
                          [USER-DISPLAY-NAME]
                          [USER-URI]
                     1*(  (FLOOR-REQUEST-ID)
                        1*(FLOOR-ID)
                          [HUMAN-READABLE-INFO]
                          [PRIORITY]
                          (REQUEST-STATUS)     )
                          [NONCE]

                   Figure 23: FloorRequestInfo format


5.3.5  FloorInfoWanted

   Floor participants and floor chairs request information about a floor
   or floors by sending a FloorInfoWanted message to the floor control
   server.  The following is the format of the FloorRequest message:











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   FloorInfoWanted =   (FIXED-HEADER)
                       (TRANSACTION-ID)
                       (USER-ID)
                      *(FLOOR-ID)
                       [NONCE]
                       [DIGEST]

                   Figure 24: FloorInfoWanted format


5.3.6  FloorInfo

   The floor control server informs floor participants and floor chairs
   about the status (e.g., the current holder) of a floor by sending
   them FloorInfo messages.  The following is the format of the
   FloorInfo message:


   FloorInfo        =       (FIXED-HEADER)
                            [TRANSACTION-ID]
                            (USER-ID)
                            [FLOOR-ID]
                         *( (FLOOR-REQUEST-ID)
                            [BENEFICIARY-ID]
                            [USER-DISPLAY-NAME]
                            [USER-URI]
                           *(FLOOR-ID)
                            [HUMAN-READABLE-INFO]
                            [PRIORITY]
                            (REQUEST-STATUS)      )
                            [NONCE]

                      Figure 25: FloorInfo format


5.3.7  ChairAction

   Floor chairs send instructions to floor control servers by sending
   ChairAction messages.  The following is the format of the ChairAction
   message:











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   ChairAction  =   (FIXED-HEADER)
                    (TRANSACTION-ID)
                    (USER-ID)
                  1*(FLOOR-ID)
                    (FLOOR-REQUEST-ID)
                    (REQUEST-STATUS)
                    [HUMAN-READABLE-INFO]
                    [NONCE]
                    [DIGEST]

                     Figure 26: ChairAction format


5.3.8  ChairActionAck

   Floor control servers confirm that they have accepted a ChairAction
   message by sending a ChairActionAck message.  The following is the
   format of the ChairActionAck message:


   ChairActionAck  =   (FIXED-HEADER)
                       (TRANSACTION-ID)
                       (USER-ID)
                       [NONCE]

                    Figure 27: ChairActionAck format


5.3.9  Hello

   Floor participants and floor chairs check the liveness of floor
   control servers by sending a Hello message.  The following is the
   format of the Hello message:


   Hello         =  (FIXED-HEADER)
                    (TRANSACTION-ID)
                    (USER-ID)
                    [NONCE]
                    [DIGEST]

                        Figure 28: Hello format


5.3.10  HelloAck

   Floor control servers confirm that they are alive on reception of a
   Hello message by sending a HelloAck message.  The following is the



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   format of the HelloAck message:


   HelloAck      =  (FIXED-HEADER)
                    (TRANSACTION-ID)
                    (USER-ID)
                    (SUPPORTED-TLVS)
                    [NONCE]

                       Figure 29: HelloAck format


5.3.11  Error

   Floor control servers inform floor participants and floor chairs
   about errors processing requests by sending them Error messages.  The
   following is the format of the Error message:


   Error              =   (FIXED-HEADER)
                          (TRANSACTION-ID)
                          (USER-ID)
                          (ERROR-CODE)
                          [NONCE]
                          [HUMAN-READABLE-INFO]


                        Figure 30: Error format


6.  Transport

   BFCP entities exchange BFCP messages using TCP connections.  TCP
   provides an in-order reliable delivery of a stream of bytes.
   Consequently, message framing is implemented in the application
   layer.  BFCP implements application-layer framing using TLVs.

   A client MUST NOT use more than one TCP connection to communicate
   with a given floor control server within a conference.  Nevertheless,
   if the same physical box handles different clients (e.g., a floor
   chair and a floor participant), which are identified by different
   User IDs, a separate connection per client is allowed.

   If a BFCP entity (a client or a floor control server) receives data
   from TCP that cannot be parsed the entity MUST close the TCP
   connection using a RESET call (send a TCP RST bit) and the connection
   SHOULD be reestablished.  Similarly, if a TCP connection cannot
   deliver a BFCP message and times out, the TCP connection SHOULD be



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   reestablished.

   The way connection reestablishment is handled depends on how the
   client obtains information to contact the floor control server (e.g.,
   using an offer/answer exchange [14]).  Once the TCP connection is
   reestablished, the client MAY resend those message it did not get a
   response for from the floor control server.

   If a floor control server detects that the TCP connection towards one
   of the floor participants is lost, it is up to the local policy of
   the floor control server what to do with the pending floor requests
   of the floor participant.  In any case, it is RECOMMENDED that the
   floor control server keeps the floor requests (i.e., does not cancel
   them) while the TCP connection is reestablished.

   If a client wishes to end its BFCP connection with a floor control
   server, the client closes (i.e., a graceful close) the TCP connection
   towards the floor control server.  If a floor control server wishes
   to end its BFCP connection with a client (e.g., the focus of the
   conference informs the floor control server that the client has been
   kicked out from the conference), the floor control server closes
   (i.e., a graceful close) the TCP connection towards the client.

7.  Lower-Layer Security

   BFCP relies on lower-layer security mechanisms to provide replay and
   integrity protection, and confidentiality.  BFCP floor control
   servers MUST support TLS [4], and BFCP clients (which include both
   floor participants and floor chairs) SHOULD support TLS.  Any BFCP
   entity MAY support other security mechanisms.

   BFCP entities that implement TLS MUST support, at a minimum, the TLS
   TLS_RSA_WITH_AES_128_CBC_SHA ciphersuite [6].

8.  Protocol Transactions

   In BFCP, there are two types of transactions: client-initiated
   transactions and server-initiated transactions (notifications).
   Client-initiated transactions consist of a request from a client to a
   floor control server and a response from the floor control server to
   the client.  The request carries a TRANSACTION-ID TLV which the floor
   control server copies into the response.  Clients use Transaction ID
   values to match responses with previously-issued requests.

   Server-initiated transactions consist of a single message from a
   floor control server to a client.  Since they do not trigger any
   response, server-initiated transactions do not have Transaction IDs
   associated with them.



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8.1  Client Behavior

   A client starting a client-initiated transaction MUST set the
   Conference ID in the FIXED-HEADER of the message to the Conference ID
   for the conference that the client obtained previously.

   The client MUST set the Transaction ID value in the TRANSACTION-ID
   TLV to a number which MUST NOT be reused in another message from the
   client until a response from the server is received for the
   transaction.  The client uses the Transaction ID value to match this
   message with the response from the floor control server.

8.2  Server Behavior

   A floor control server sending a response within a client-initiated
   transaction MUST copy the Conference ID, the TRANSACTION-ID TLV, and
   the USER-ID TLV from the request received from the client into the
   response.  Server-initiated transactions MUST NOT contain a
   TRANSACTION-ID TLV.

9.  Authentication and Authorization

   BFCP uses the DIGEST TLV to provide client authentication.  The
   DIGEST TLV contains an HMAC-SHA1 [1] of the BFCP message.  The use of
   SHA1 implies that the length of the HMAC is 20 bytes.  The text used
   as input to HMAC is the BFCP message, including the FIXED-HEADER, up
   to and including the TLV preceding the DIGEST TLV.  This text is then
   padded with zeroes so as to be a multiple of 64 bytes.  As a result,
   the DIGEST TLV MUST be the last attribute in any BFCP message.  The
   key used as input to HMAC is the secret shared between the server and
   the user identified by the USER-ID TLV in the message.

9.1  Client Behavior

   Clients can authenticate floor control servers by checking the floor
   control server's certificate when the TLS connection is established
   between them.

   To achieve client authentication, a client needs to prove to the
   floor control server that the client can produce a DIGEST TLV for a
   message using their shared secret and that the message is fresh (to
   avoid replay attacks).  Clients prove the freshness of a message by
   including a NONCE TLV in the message.  The NONCE TLV is the second to
   last TLV in the message (the last one is the DIGEST TLV).

   The nonce to be places in the NONCE TLV by the client is typically
   provided by the floor control server in an Error response --
   typically with Error Code 7 (DIGEST TLV Required) or 6 (Invalid



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   Nonce).  Additionally, as an optimization, the floor control server
   can provide a client with a NONCE to be used in the first message
   generated by the client using an out-of-band mechanism (e.g., using
   an offer/answer exchange as described in [14]).  This way, the client
   does not need to generate an initial BFCP message only to have it
   rejected by the floor control server with an Error response
   containing a nonce.

   A client that obtains a nonce out-of-band SHOULD add a NONCE TLV and
   a DIGEST TLV to the first message it sends to the floor control
   server.  Furthermore, if any client generates a message without a
   DIGEST TLV and receives an Error response with Error Code 7 (DIGEST
   TLV Required), the client SHOULD re-send the message with a DIGEST
   TLV and a NONCE TLV with the nonce received in the Error response.

   If after sending a message with a DIGEST TLV, a client receives an
   Error response with Error Code 6 (Invalid Nonce), the client SHOULD
   re-send the message using the new nonce received in the Error
   response.  If the Error Code is 1 (Authentication Failed) instead,
   the client MUST NOT send further messages to the floor control server
   until it has obtained a different (hopefully valid) shared secret
   than the one used in the original message.

   If a client receives a nonce in a message from the floor control
   server, the client SHOULD add a NONCE TLV with this nonce and a
   DIGEST TLV to its next message to the floor control server.

9.2  Floor Control Server Behavior

   Before accepting any BFCP message, the floor control server SHOULD
   authenticate the client.  If the floor control server receives a
   message without DIGEST TLV from an unauthenticated client, the floor
   control server responds with an Error message with Error Code 7
   (DIGEST TLV Required).  The floor control message MUST include a
   NONCE TLV with a nonce value that is unguessable by attackers.

   When a floor control server receives a BFCP message with a DIGEST
   TLV, it checks whether the NONCE TLV carries a nonce which was
   generated by the floor control server for this client and which still
   has not expired.  If the nonce is not valid, authentication is
   considered to have failed, in which case the floor control server
   SHOULD return an Error message with Error Code 6 (Invalid Nonce) with
   a new nonce in a NONCE TLV.

   If the nonce is valid, the floor control server calculates the
   HMAC-SHA1 [1] of the message excluding the DIGEST TLV.  The key used
   as input to HMAC is the secret shared between the server and the user
   identified by the USER-ID TLV in the message.  If the resulting value



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   is the same as the one in the DIGEST TLV, authentication is
   considered successful.

   If the resulting value is different than the one in the DIGEST TLV,
   authentication is considered to have failed, in which case the server
   SHOULD return an Error message, as described in Section 13.7, with
   Error Code 1 (Authentication Failed).  Messages from a client that
   cannot be authenticated MUST NOT be processed further.

   Floor control servers may include a NONCE TLV in their responses to
   provide the nonce to be used in the next message by the client.
   However, when TLS is used, floor control servers typically
   authenticate only the first message sent over the TLS connection.

   After authenticating a BCFP message, the floor control server checks
   whether or not the client is authorized to perform the operation it
   is requesting.  If the client is not authorized to perform the
   operation being requested, the floor control server generates an
   Error message, as described in Section 13.7, with an Error code with
   a value of 4 (Unauthorized Operation).  Messages from a client that
   cannot be authorized MUST NOT be processed further.

10.  Floor Participant Operations

   This section specifies how floor participants can perform different
   operations, such as requesting a floor, using the protocol elements
   described in earlier sections.  Section 11 specifies operations that
   are specific to floor chairs, such as instructing the floor control
   server to grant or revoke a floor, and Section 12 specifies
   operations that can be performed by any client (i.e., both floor
   participants and floor chairs).

10.1  Requesting a Floor

   A floor participant that wishes to request one or more floors does so
   by sending a FloorRequest message to the floor control server.

10.1.1  Sending a FloorRequest Message

   The ABNF in Section 5.3.1 describes the TLVs that a FloorRequest
   message can contain.  In addition, the ABNF specifies normatively
   which of these TLVs are mandatory, and which ones are optional.

   The floor participant sets the Conference ID in the FIXED-HEADER and
   the TRANSACTION-ID TLV following the rules given in Section 8.1.
   Additionally, the floor participant follows the rules in Section 9.1
   which relate to the authentication of the message (i.e., to the
   DIGEST TLV).



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   The floor participant must insert a USER-ID TLV, which will be used
   by the floor control server to authenticate and authorize the
   request.  If the sender of the FloorRequest message (identified by
   the USER-ID TLV) is not the participant that would eventually get the
   floor (i.e., a third party floor request), the sender SHOULD add a
   BENEFICIARY-ID TLV to the message identifying the beneficiary of the
   floor.

      Note that the name space for both the User ID and the Beneficiary
      ID is the same.  That is, a given participant is identified by a
      single 16-bit value that can be used in USER-ID and in
      BENEFICIARY-ID TLVs.

   The floor participant must insert at least one FLOOR-ID TLV in the
   FloorRequest message.  If the client inserts more than one FLOOR-ID
   TLVs, the floor control server will treat all the floor requests as
   an atomic package.  That is, the floor control server will either
   grant or deny all the floors in the FloorRequest message.

   The floor participant may use a HUMAN-READABLE-INFO TLV to state the
   reason why the floor or floors are being requested.  The Text field
   in the HUMAN-READABLE-INFO TLV is intended for human consumption.

   The floor participant may request the server to handle the floor
   request with a certain priority using a PRIORITY TLV.

10.1.2  Receiving a Response

   A message from the floor control server is considered to be a
   response to the FloorRequest message if the message from the floor
   control server has the same Conference ID, Transaction ID, and User
   ID as the FloorRequest message, as described in Section 8.1.

   The successful processing of a FloorRequest message at the floor
   control server involves generating one or several FloorRequestInfo
   messages.  The floor participant obtains a Floor Request ID in a
   FLOOR-REQUEST-ID TLV in the first FloorRequestInfo message from the
   floor control server.  Subsequent FloorRequestInfo messages from the
   floor control server regarding the same floor request will carry the
   same Floor Request ID as the initial FloorRequestInfo message.  This
   way, the floor participant can associate subsequent incoming
   FloorRequestInfo messages with the ongoing floor request.

   The floor participant obtains information about the status of the
   floor request in the REQUEST-STATUS TLV of each of the
   FloorRequestInfo messages received from the floor control server.  If
   the Request Status value is Granted, all the floors that were
   requested in the FloorRequest message have been granted.  If the



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   Request Status value is Denied, all the floors that were requested in
   the FloorRequest message have been denied.  The HUMAN-READABLE-INFO
   TLV, if present, provides extra information which the floor
   participant MAY display to the user.

   A floor request is considered to be ongoing while it is in the
   Pending, Accepted, or Granted states.

   If the response is an Error message, the floor control server could
   not process the FloorRequest message for some reason, which is
   described in the Error message.

10.2  Cancelling a Floor Request and Releasing a Floor

   A floor participant that wishes to cancel an ongoing floor request
   does so by sending a FloorRelease message to the floor control
   server.  The FloorRelease message is also used by floor participants
   that hold a floor and would like to release it.

10.2.1  Sending a FloorRelease Message

   The ABNF in Section 5.3.2 describes the TLVs that a FloorRelease
   message can contain.  In addition, the ABNF specifies normatively
   which of these TLVs are mandatory, and which ones are optional.

   The floor participant sets the Conference ID in the FIXED-HEADER and
   the TRANSACTION-ID TLV following the rules given in Section 8.1.
   Additionally, the floor participant follows the rules in Section 9.1
   which relate to the authentication of the message (i.e., to the
   DIGEST TLV).  The floor participant must insert a USER-ID TLV, which
   will be used by the floor control server to authenticate and
   authorize the request.

      Note that the FloorRelease message is used to release a floor or
      floors that were granted and to cancel ongoing floor requests
      (from the protocol perspective both are ongoing floor requests).
      Using the same message in both situations helps resolve the race
      condition that occurs when the FloorRelease message and the
      FloorGrant message cross each other on the wire.

   The floor participant uses the FLOOR-REQUEST-ID that was received in
   the response to the FloorRequest message that the FloorRelease
   message is cancelling.

      Note that if the floor participant requested several floors as an
      atomic operation (i.e., in a single FloorRequest message), all the
      floors are released as an atomic operation as well (i.e., all are
      released at the same time).



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10.2.2  Receiving a Response

   A message from the floor control server is considered to be a
   response to the FloorRelease message if the message from the floor
   control server has the same Conference ID, Transaction ID, and User
   ID as the FloorRequest message, as described in Section 8.1.

   If the response is a FloorRequestInfo message, the Request Status
   value in the REQUEST-STATUS-TLV will be Cancelled or Released.

   If the response is an Error message, the floor control server could
   not process the FloorRequest message for some reason, which is
   described in the Error message.

   It is possible that the FloorRelease message crosses on the wire with
   a FloorRequestInfo message from the server with a Request Status
   different from Cancelled or Released.  In any case, such a
   FloorRequestInfo message will not be a response to the FloorRelease
   message, because its Transaction ID will not match that of the
   FloorRelease.

11.  Chair Operations

   This section specifies how floor chairs can instruct the floor
   control server to grant or revoke a floor using the protocol elements
   described in earlier sections.

   Floor chairs that wish to send instructions to a floor control server
   do so by sending a ChairAction message.

11.1  Sending a ChairAction Message

   The ABNF in Section 5.3.7 describes the TLVs that a ChairAction
   message can contain.  In addition, the ABNF specifies normatively
   which of these TLVs are mandatory, and which ones are optional.

   The floor chair sets the Conference ID in the FIXED-HEADER and the
   TRANSACTION-ID TLV following the rules given in Section 8.1.
   Additionally, the floor chair follows the rules in Section 9.1 which
   relate to the authentication of the message (i.e., to the DIGEST
   TLV).  The floor chair must insert a USER-ID TLV, which will be used
   by the floor control server to authenticate and authorize the
   request.

   The ChairAction message contains instructions that apply to one or
   more floors within a particular floor request.  The floor or floors
   are identified by FLOOR-ID TLVs and the floor request is identified
   by a FLOOR-REQUEST-ID TLV, which are carried in the ChairAction



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   message.

      For example, if a floor request consists of two floors that depend
      on different floor chairs, each floor chair will grant its floor
      within the floor request.  Once both chairs have granted their
      floor, the floor control server will grant the floor request as a
      whole.  On the other hand, if one of the floor chairs denies its
      floor, the floor control server will deny the floor request as a
      whole, regardless of the other floor chair's decision.

   The floor chair provides the new status for one or more floors within
   the floor request using a REQUEST-STATUS TLV.  If the new status of
   the floor request is Accepted, the floor chair MAY use the Queue
   Position field to provide a queue position for the floor request.  If
   the floor chair does not wish to provide a queue position, all the
   bits of the Queue Position field SHOULD be set to zero.  The floor
   chair SHOULD use the Status Revoked to revoke a floor that was
   granted (i.e., Granted status) and the Status Denied to reject floor
   requests in any other status (e.g., Pending and Accepted).

      Note that a floor request may involve several floors and that a
      ChairAction message may only deal with a subset of these floors
      (e.g., if a single floor chair is not authorized to manage all the
      floors).  In this case, the REQUEST-STATUS that the floor chair
      provides in the ChairAction message might not be the actual status
      that the floor request gets at the server.  The floor control
      server will combine the instructions received from the different
      floor chairs to come up with the actual status of the floor
      request.

   The floor chair may use a HUMAN-READABLE-INFO TLV to state the reason
   why the floor or floors are being accepted, granted, or revoked.  The
   Text in the HUMAN-READABLE-INFO TLV is intended for human
   consumption.

11.2  Receiving a Response

   A message from the floor control server is considered to be a
   response to the ChairAction message if the message from the server
   has the same Conference ID, Transaction ID, and User ID as the
   ChairAction message, as described in Section 8.1.

   A ChairActionAck message from the floor control server confirms that
   the floor control server has accepted the ChairAction message.  An
   Error message indicates that the floor control server could not
   process the ChairAction message for some reason, which is described
   in the Error message.




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12.  General Client Operations

   This section specifies operations that can be performed by any
   client.  That is, they are not specific to floor participants or
   floor chairs.  They can be performed by both.

12.1  Requesting Information about Floors

   A client can obtain information about the status of a floor or floors
   in different ways, which include using BFCP and using out-of-band
   mechanisms.  Clients using BFCP to obtain such information use the
   procedures described in this section.

   Clients request information about the status of one or several floors
   by sending a FloorInfoWanted message to the floor control server.

12.1.1  Sending a FloorInfoWanted Message

   The ABNF in Section 5.3.5 describes the TLVs that a FloorInfoWanted
   message can contain.  In addition, the ABNF specifies normatively
   which of these TLVs are mandatory, and which ones are optional.

   The client sets the Conference ID in the FIXED-HEADER and the
   TRANSACTION-ID TLV following the rules given in Section 8.1.
   Additionally, the client follows the rules in Section 9.1 which
   relate to the authentication and the protection of the integrity of
   the message (i.e., to the DIGEST TLV).  The client must insert a
   USER-ID TLV, which will be used by the floor control server to
   authenticate and authorize the request.

   The client inserts in the message all the Floor IDs it wants to
   receive information about.  The floor control server will send
   periodic information about all these floors.  If the client does not
   want to receive information about a particular floor any longer, it
   sends a new FloorInfoWanted message removing the FLOOR-ID of this
   floor.  If the client does not want to receive information about any
   floor any longer, it sends a FloorInfoWanted message with no FLOOR-ID
   TLV.

12.1.2  Receiving a Response

   A message from the floor control server is considered to be a
   response to the FloorInfoWanted message if the message from the floor
   control server has the same Conference ID, Transaction ID, and User
   ID as the FloorRequest message, as described in Section 8.1.

   On reception of the FloorInfoWanted message, the floor control server
   will respond with a FloorInfo message or with an Error message.  If



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   the response is a FloorInfo message, it will contain information
   about one of the floors the client requested information about.  If
   the client did not include any FLOOR-ID TLV in its FloorInfoWanted
   message, the FloorInfo message from the floor control server will not
   include any either.

   FloorInfo messages which carry information about a floor contain a
   FLOOR-ID TLV that identifies the floor.  After this TLV, FloorInfo
   messages contain information about existing (one or more) floor
   request that relate to that floor.  The information about each
   particular floor request consist of a FLOOR-REQUEST-ID TLV that
   identifies the floor request followed by a set of TLVs that provide
   information about the floor request.

   After the first FloorInfo, the floor control server will continue
   sending FloorInfo messages periodically informing the client about
   changes on the floors the client requested information about.

12.2  Requesting Information about Floor Requests

   A client can obtain information about the status of one or several
   floor requests in different ways, which include using BFCP and using
   out-of-band mechanisms.  Clients using BFCP to obtain such
   information use the procedures described in this section.

   Clients request information about the current status of one or
   several floor requests by sending a FloorRequestInfoWanted message to
   the floor control server.

      Requesting information about a particular floor request is useful
      in a number of situations.  For example, on reception of a
      FloorRequest message, a floor control server may choose to return
      FloorRequestInfo messages only when the floor request changes its
      state (e.g., from Accepted to Granted), but not when the floor
      request advances in its queue.  In this situation, if the user
      requests it, the floor participant can use a
      FloorRequestInfoWanted message to poll the floor control server
      for the status of the floor request.
      FloorRequestInfoWanted messages can also be used to request
      information on all the floor requests associated with a floor
      participant.  For example, a floor participant, after experiencing
      connectivity problems (e.g., its TCP connection with the floor
      control server was down for a while and eventually was
      re-established), may need to request information about all the
      still existing floor requests associated to the floor participant.






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12.2.1  Sending a FloorRequestInfoWanted Message

   The ABNF in Section 5.3.3 describes the TLVs that a
   FloorRequestInfoWanted message can contain.  In addition, the ABNF
   specifies normatively which of these TLVs are mandatory, and which
   ones are optional.

   The client sets the Conference ID in the FIXED-HEADER and the
   TRANSACTION-ID TLV following the rules given in Section 8.1.
   Additionally, the client follows the rules in Section 9.1 which
   relate to the authentication of the message (i.e., to the DIGEST
   TLV).  The client must insert a USER-ID TLV, which will be used by
   the floor control server to authenticate and authorize the request.

   If the client wants to request the status of a single floor request,
   it MUST insert a FLOOR-REQUEST-ID TLV that identifies the floor
   request at the floor control server.

   The client can also request information about all the ongoing floor
   requests associated with a particular participant.  In this case, the
   client MUST NOT insert a FLOOR-REQUEST-ID TLV.  If the beneficiary of
   the floor requests the client is requesting information about is not
   the client issuing the FloorRequestInfoWanted message (which is
   identified by the USER-ID TLV in the message) the client MUST insert
   a BENEFICIARY-ID TLV.

12.2.2  Receiving a Response

   A message from the floor control server is considered to be a
   response to the FloorRequestInfoWanted message if the message from
   the floor control server has the same Conference ID, Transaction ID,a
   nd User ID as the FloorRequestInfoWanted message, as described in
   Section 8.1.

   If the response is a FloorRequestInfo message, the client obtains
   information about the status of the FloorRequest the client requested
   information about in a REQUEST-STATUS TLVs.  If the client requested
   information about several floor requests, the FloorRequestInfo
   message will carry several FLOOR-REQUEST-ID TLVs.  Each
   FLOOR-REQUEST-ID TLV will be followed by TLVs (which will include a
   REQUEST-STATUS TLV) providing information about the floor request
   identified by the FLOOR-REQUEST-ID TLV.

   If the response is an Error message, the floor control server could
   not process the FloorRequestInfoWanted message for some reason, which
   is described in the Error message.





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12.3  Obtaining the Capabilities of a Floor Control Server

   A client that wishes to obtain the capabilities of a floor control
   server does so by sending a Hello message to the floor control
   server.

12.3.1  Sending a Hello Message

   The ABNF in Section 5.3.9 describes the TLVs that a Hello message can
   contain.  In addition, the ABNF specifies normatively which of these
   TLVs are mandatory, and which ones are optional.

   The client sets the Conference ID in the FIXED-HEADER and the
   TRANSACTION-ID TLV following the rules given in Section 8.1.
   Additionally, the client follows the rules in Section 9.1 which
   relate to the authentication and the protection of the integrity of
   the message (i.e., to the DIGEST TLV).  The client must insert a
   USER-ID TLV, which will be used by the floor control server to
   authenticate and authorize the request.

12.3.2  Receiving Responses

   A message from the floor control server is considered a response to
   the Hello message by the client if the message from the floor control
   server has the same Conference ID, Transaction ID, and User ID as the
   Hello message, as described in Section 8.1.

   If the response is a HelloAck message, the floor control server could
   process successfully the Hello message.  The SUPPORTED-TLVS TLV
   indicates which TLVs are supported by the server.

   If the response is an Error message, the floor control server could
   not process the Hello message for some reason, which is described in
   the Error message.

13.  Floor Control Server Operations

   This section specifies how floor control servers can perform
   different operations, such as granting a floor, using the protocol
   elements described in earlier sections.

   On reception of a message from a client, the floor control server
   MUST check whether or not the value of the Conference ID matched an
   existing conference.  If it does not, the floor control server SHOULD
   send an Error message, as described in Section 13.7, with Error code
   0 (Conference does not Exist).

   On reception of a message from a client, the floor control server



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   follows the rules in Section 9.2, which relate to the authentication
   of the message.

   On reception of a message from a client, the floor control server
   MUST check whether or not it understands all the mandatory ( 'M' bit
   set) TLVs in the message.  If the floor control server does not
   understand all of them, the floor control server SHOULD send an Error
   message, as described in Section 13.7, with Error code 2
   (Authentication Failed).  The Error message SHOULD list the TLVs that
   were not understood.

13.1  Reception of a FloorRequest Message

   On reception of a FloorRequest message, the floor control server
   follows the rules in Section 9.2 which relate to client
   authentication and authorization.  If while processing the
   FloorRequest message, the floor control server encounters an error,
   it SHOULD generate an Error response following the procedures
   described in Section 13.7

      BFCP allows floor participants to have several ongoing floor
      requests for the same floor (e.g., the same floor participant can
      occupy more than one position in a queue at the same time).  A
      floor control server that only supports a certain number of
      ongoing floor requests per floor participant (e.g., one) can use
      Error Code 9 (You have Already Reached the Maximum Number of
      Ongoing Floor Requests for this Floor) to inform the floor
      participant.

13.1.1  Generating the First FloorRequestInfo Message

   The successful processing of a FloorRequest message by a floor
   control server involves generating one or several FloorRequestInfo
   messages, the first of which SHOULD be generated as soon as possible.
   If the floor control server cannot accept, grant, or deny the floor
   request right away (e.g., a decision from a chair is needed), it
   SHOULD use a Request Status value of Pending in the REQUEST-STATUS
   TLV of the first FloorRequestInfo message it generates.

      The policy a floor control server follows to grant or deny floors
      is outside the scope of this document.  A given floor control
      server may perform these decisions automatically while another may
      contact a human acting as a chair everytime a decision needs to be
      made.

   The floor control server copies the Conference ID, the
   TRANSACTION-ID, and the USER-ID TLVs from the FloorRequest into the
   FloorRequestInfo, as described in Section 8.2.  Additionally, the



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   floor control server copies (if present) the BENEFICIARY-ID TLV from
   the FloorRequest into the FloorRequestInfo.

   The floor control server MUST assign an identitifier that is unique
   within the conference to this floor request, and insert it in a
   FLOOR-REQUEST-ID TLV into the FloorRequestInfo message.  This
   indentifier will be used by the floor participant (or by a chair or
   chairs) to refer to this specific floor request in the future.

   The floor control server copies the FLOOR-ID TLVs from the
   FloorRequest into the FloorRequestInfo.  These FLOOR-ID TLVs identify
   the floors being requested (i.e., the floors associated with this
   particular floor request).

   The floor control server also copies (if present) the PRIORITY TLV
   from the FloorRequest into the FloorRequestInfo.  The Priority value
   requested by the floor participant is only a hint, and does not
   necessarily need to be taken into consideration to decide whether to
   grant or not the floor request.

13.1.2  Generation of Subsequent FloorRequestInfo Messages

   A floor request is considered to be ongoing as long as it is not in
   the Cancelled, Released, or Revoked states.  If the REQUEST-STATUS
   TLV of the first FloorRequestInfo message generated by the floor
   control server did not indicate any of these states, the floor
   control server will need to send subsequent FloorRequestInfo
   messages.

   When the status of the floor request changes, the floor control floor
   control server SHOULD send new FloorRequestInfo messages with the
   appropriate Request Status.  These FloorRequestInfo messages MUST
   contain a FLOOR-REQUEST-ID TLV equal to the one sent in the first
   FloorRequestInfo message, but MUST NOT contain any TRANSACTION-ID
   TLV.  (The Floor Request ID identifies the floor request the
   FloorRequestInfo applies to.)

   The FIXED-HEADER and the rest of the TLVs (except for the
   HUMAN-READABLE-INFO TLV) are the same as in the first
   FloorRequestInfo message.

      The rate at which the floor control server sends FloorRequestInfo
      messages is a matter of local policy.  A floor control server may
      choose to send a new FloorRequestInfo message every time the floor
      request moves in the floor request queue while another may choose
      to only send a new FloorRequestInfo message when the floor request
      is Granted or Denied.




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   The floor control server may add a HUMAN-READABLE-INFO TLV to any of
   the FloorRequestInfo messages it generates to provide extra
   information about its decisions regarding the floor request (e.g.,
   why it was denied).

      Floor participants and floor chairs may request to be informed
      about the status of a floor following the procedures in Section
      12.1.  If the processing of a floor request changes the status of
      a floor (e.g., the floor request is granted and consequently the
      floor has a new holder), the floor control server needs to follow
      the procedures in Section 13.4 to inform the clients that have
      requested that information

   The floor control server can discard the state information about a
   particular floor request when this reaches a status of Cancelled,
   Released, or Revoked.

13.2  Reception of a FloorRequestInfoWanted Message

   On reception of a FloorRequestInfoWanted message, the floor control
   server follows the rules in Section 9.2 which relate to client
   authentication and authorization.  If while processing the
   FloorRequestInfoWanted message, the floor control server encounters
   an error, it SHOULD generate an Error response following the
   procedures described in Section 13.7

   The successful processing of a FloorRequestInfoWanted message by a
   floor control server involves generating a FloorRequestInfo message,
   which SHOULD be generated as soon as possible.

   The floor control server copies the Conference ID, the
   TRANSACTION-ID, and the USER-ID TLVs from the FloorRequestInfoWanted
   message into the FloorRequestInfo message, as described in Section
   8.2.

13.2.1  Information on a Single Floor Request

   If the FloorRequestInfoWanted message carries a FLOOR-REQUEST-ID, the
   sender of the message is requesting information about the floor
   request identified by the FLOOR-REQUEST-ID TLV.  The floor control
   server copies the FLOOR-REQUEST-ID TLV from the
   FloorRequestInfoWanted message into the FloorRequestInfo message.

   The floor control server adds FLOOR-ID TLVs to the FloorRequestInfo
   message identifying the floors being requested (i.e., the floors
   associated with the floor request identified by the FLOOR-REQUEST-ID
   TLV).




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   The floor control server may also add a PRIORITY TLV with the
   Priority value requested for the floor request and a
   HUMAN-READABLE-INFO TLV with extra information about the floor
   request.

   The floor control server adds a REQUEST-STATUS TLV with the current
   status of the floor request.

13.2.2  Information on the Floor Requests Associated to a Participant

   If the FloorRequestInfoWanted message does not carry a
   FLOOR-REQUEST-ID TLV, the sender of the message is requesting
   information about all the floor requests from a given participant.
   This participant is identified by a BENEFICIARY-ID TLV or, in the
   absence of a BENEFICIARY-ID TLV, by a USER-ID TLV.

   The floor control server copies (if present) the BENEFICIARY-ID TLV
   from the FloorRequestInfoWanted message into the FloorRequestInfo
   message.  Additionally, the floor control server may provide extra
   information about the participant by adding a USER-DISPLAY-NAME TLV,
   a USER-URI TLV, or both to the FloorRequestInfo message.

   The floor control server adds a FLOOR-REQUEST-ID TLV for each floor
   request associated to the participant.  Each FLOOR-REQUEST-ID TLV is
   followed by a number of TLVs which provide information about the
   floor request.  The floor control server generates the TLVs that
   follow each FLOOR-REQUEST-ID following the rules in Section 13.2.1

13.3  Reception of a FloorRelease Message

   On reception of a FloorRelease message, the floor control server
   follows the rules in Section 9.2 which relate to client
   authentication and authorization.  If while processing the
   FloorRelease message, the floor control server encounters an error,
   it SHOULD generate an Error response following the procedures
   described in Section 13.7

   The successful processing of a FloorRelease message by a floor
   control server involves generating a FloorRequestInfo message, which
   SHOULD be generated as soon as possible.

   The floor control server copies the Conference ID, the
   TRANSACTION-ID, and the USER-ID TLVs from the FloorRelease message
   into the FloorRequestInfo message, as described in Section 8.2.

   The FloorRelease message identifies the floor request it applies to
   using a FLOOR-REQUEST-ID.  If the beneficiary of the floor request is
   not the participant identified by the USER-ID TLV in the FloorRelease



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   message, the floor control server adds a BENEFICIARY-ID TLV to the
   FloorRequestInfo message identifying the beneficiary of the floor
   request.  Additionally, the floor control server may provide extra
   information about the beneficiary of the floor request by adding a
   USER-DISPLAY-NAME TLV, a USER-URI TLV, or both to the
   FloorRequestInfo message.

   The floor control server copies the FLOOR-REQUEST-ID TLV from the
   FloorRelease message into the FloorRequestInfo message.

   The floor control server adds FLOOR-ID TLVs to the FloorRequestInfo
   message identifying the floors being requested (i.e., the floors
   associated with the floor request identified by the FLOOR-REQUEST-ID
   TLV).

   The floor control server may also add a PRIORITY TLV with the
   Priority value requested for the floor request and a
   HUMAN-READABLE-INFO TLV with extra information about the floor
   request.

   The floor control server adds a REQUEST-STATUS TLV to the
   FloorRequestInfo message.  The Request Status value SHOULD be
   Released, if the floor (or floors) had been previously granted, or of
   Cancelled, if the floor (or floors) had not been previously granted.

13.4  Reception of a FloorInfoWanted Message

   On reception of a FloorInfoWanted message, the floor control server
   follows the rules in Section 9.2 which relate to client
   authentication.  If while processing the FloorRelease message, the
   floor control server encounters an error, it SHOULD generate an Error
   response following the procedures described in Section 13.7

   A floor control server receiving a FloorInfoWanted message from a
   client SHOULD keep this client informed about the status of the
   floors identified by FLOOR-ID TLVs in the FloorInfoWanted message.
   Floor Control Servers keep clients informed by using FloorInfo
   messages.

   An individual FloorInfo message carries information about a single
   floor.  So, when a FloorInfoWanted message requests information about
   more than one floor, the floor control server needs to send separate
   FloorInfo messages for different floors.

   The information FloorInfoWanted messages carry may depend on the user
   requesting the information.  For example, a chair may be able to
   receive information about pending requests while a regular user may
   not be authorized to do so.



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13.4.1  Generation of the First FloorInfo Message

   The successful processing of a FloorInfoWanted message by a floor
   control server involves generating one or several FloorInfo messages,
   the first of which SHOULD be generated as soon as possible.

   The floor control server copies the Conference ID, the
   TRANSACTION-ID, and the USER-ID TLVs from the FloorInfoWanted message
   into the FloorInfo message, as described in Section 8.2.

   If the FloorInfoWanted message did not contain any FLOOR-ID TLV, the
   floor control server sends the FloorInfo message without adding any
   additional TLV and does not send any subsequent FloorInfo message to
   the floor participant.

   If the FloorInfoWanted message contained one or more FLOOR-ID TLVs,
   the floor control server chooses one among them and adds this
   FLOOR-ID TLV to the FloorInfo message.  The floor control server adds
   a FLOOR-REQUEST-ID TLV for each floor request associated to the
   floor.  Each FLOOR-REQUEST-ID TLV is followed by a number of TLVs
   which provide information about the floor request.

   For each FLOOR-REQUEST-ID TLV, the floor control server may add a
   BENEFICIARY-ID TLV identifying the requester of the floor and a
   USER-DISPLAY-NAME TLV, a USER-URI TLV, or both providing information
   about the requester.  Additionally, the floor control server adds
   FLOOR-ID TLVs to the FloorInfo message identifying the floors being
   requested (i.e., the floors associated with the floor request
   identified by the FLOOR-REQUEST-ID TLV).

   The floor control server may also add a PRIORITY TLV with the
   Priority value requested for the floor request and a
   HUMAN-READABLE-INFO TLV with extra information about the floor
   request.

   The floor control server adds a REQUEST-STATUS TLV with the current
   status of the floor request.

13.4.2  Generation of Subsequent  FloorInfo Messages

   If the FloorInfoWanted message carried more than one FLOOR-ID TLV,
   the floor control server SHOULD generate a FloorInfo message for each
   of them (except for the FLOOR-ID TLV chosen for the first FloorInfo
   message) as soon as possible.  These FloorInfo messages are generated
   following the same rules as for the first FloorInfo message (see
   Section 13.4.1, but without adding a TRANSACTION TLV.

   After generating these messages, the floor control server sends



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   FloorInfo messages periodically keeping the client informed about all
   the floors the client requested information about.  These messages
   MUST NOT carry a TRANSACTION-ID TLV.

      The rate at which the floor control server sends FloorInfo
      messages is a matter of local policy.  A floor control server may
      choose to send a new FloorInfo message every time a new floor
      request arrives while another may choose to only send a new
      FloorInfo message when a new floor request is Granted.

13.5  Reception of a ChairAction Message

   On reception of a ChairAction message, the floor control server
   follows the rules in Section 9.2 which relate to client
   authentication and authorization.  If while processing the
   ChairAction message, the floor control server encounters an error, it
   SHOULD generate an Error response following the procedures described
   in Section 13.7

   The successful processing of a ChairAction message by a floor control
   server involves generating a ChairActionAck message, which SHOULD be
   generated as soon as possible.

   The floor control server copies the Conference ID, the
   TRANSACTION-ID, and the USER-ID TLVs from the ChairAction message
   into the ChairActionAck message, as described in Section 8.2.

   The floor control server needs to take into consideration the
   operation requested in the ChairAction message (e.g., granting a
   floor), but does not necessarily need to perform it as requested by
   the floor chair.  The operation that the floor control server
   performs depends on the ChairAction message and on the internal state
   of the floor control server.

   For example, a floor chair may send a ChairAction message granting a
   floor which was requested as part of an atomic floor request
   operation that involved several floors.  Even if the chair
   responsible for one of the floors instructs the floor control server
   to grant the floor, the floor control server will not grant it until
   the chairs responsible for the other floors agree to grant them as
   well.

   So, the floor control server is ultimately responsible to keep a
   coherent floor state using instructions from floor chairs as input to
   this state.

   If the new Status in the ChairAction message is Accepted and all the
   bits of the Queue Position field are zero, the floor chair is



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   requesting the floor control server to assign a queue position (e.g.,
   the last in the queue) to the floor request based on the local policy
   of the floor control server.  (Of course, such a request only applies
   in case the floor control server implements a queue.)

13.6  Reception of a Hello Message

   On reception of a Hello message, the floor control server follows the
   rules in Section 9.2 which relate to client authentication.  If while
   processing the Hello message, the floor control server encounters an
   error, it SHOULD generate an Error response following the procedures
   described in Section 13.7

   The successful processing of a Hello message by a floor control
   server involves generating a HelloAck message, which SHOULD be
   generated as soon as possible.  The floor control server copies the
   Conference ID, the TRANSACTION-ID, and the USER-ID TLVs from the
   Hello into the HelloAck, as described in Section 8.2.

   The floor control server adds a SUPPORTED-TLVS TLV to the HelloAck
   message listing all the TLVs supported by the floor control server.

13.7  Error Message Generation

   Error messages are always sent in response to a previous message from
   the client as part of a client-initiated transaction.  The ABNF in
   Section 5.3.11 describes the TLVs that an Error message can contain.
   In addition, the ABNF specifies normatively which of these TLVs are
   mandatory, and which ones are optional.

   The floor control server copies the Conference ID, the
   TRANSACTION-ID, and the USER-ID TLVs from the message from the client
   into the Error message, as described in Section 8.2.

   The floor control server adds an ERROR-CODE TLV to the Error message.
   The ERROR-CODE TLV contains an Error Code from Table 4.
   Additionally, the floor control server may add a HUMAN-READABLE-INFO
   TLV with extra information about the error.

14.  Security Considerations

   BFCP uses message signatures to provide client authentication and TLS
   to provide floor control server authentication, replay and integrity
   protection, and confidentiality.  It is RECOMMENDED that TLS with
   non-null encryption is always used and that the first message from a
   client over a given TLS connection is signed using the DIGEST TLV.
   In any case, clients and floor control servers MAY use other security
   mechanisms as long as they provide similar security properties.



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   The remainder of this Section analyzes some of the threats against
   BFCP and how they are addressed.

   An attacker may attempt to impersonate a client (a floor participant
   or a floor chair) in order to generate forged floor requests or to
   grant or deny existing floor requests.  Client impersonation is
   avoided by having clients sign their messages.  A nonce is included
   in the signature to ensure the freshness of the message.  If the
   client is using a TLS connection to communicate with the floor
   control server, it is enough that the client signs its first message
   over the TLS connection.  The floor control server assumes that
   attackers cannot hickjack the TLS connection and, therefore, that
   subsequent messages over the TLS connection come from the client that
   was initially authenticated.

   An attacker may attempt to impersonate a floor control server.  A
   successful attacker would be able to make clients think that they
   hold a particular floor so that they would try to access a resource
   (e.g., sending media) without having legitimate rights to access it.
   Floor control server impersonation is avoided by having floor control
   servers present their server certificates at TLS connection
   establishment time.

   Attackers may attempt to modify messages exchanged by a client and a
   floor control server.  The integrity protection provided by TLS
   connections prevents this attack.

   An attacker may attempt to fetch a valid message sent by a client to
   a floor control server and replay it at a later point.  If the
   attacker attempts to replay it over the TLS connection between the
   client and the floor control server, TLS mechanisms discard it at the
   receiver side.  Still, if the message was signed, the attacker may
   attempt to establish a new TLS connection with the floor control
   server and replay the message over the new connection.  Using TLS
   confidentiality prevents this attack because the attacker cannot
   access the contents of the message in the first place.  Additionally,
   if the attacker attempts to replay the encrypted message over the new
   connection, TLS mechanisms would discard it at the receiver side.
   Therefore, it is strongly RECOMMENDED that TLS is used with a
   non-null encryption algorithm.

   Attackers may attempt to pick messages from the network to get access
   to confidential information between the floor control server and a
   client (e.g., why a floor request was denied).  TLS confidentiality
   prevents this attack.






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15.  IANA Considerations

   This document instructs the IANA to create a new registry for BFCP
   parameters called "Binary Floor Control Protocol (BFCP) Parameters".
   This new registry has a number of subregistries, which are described
   in the following Sections

15.1  Attribute Subregistry

   This Section establishes the Attribute subregistry under the BFCP
   Parameters registry.  As per the terminology in RFC 2434 [5], the
   registration policy for BFCP attributes shall be "Specification
   Required".  For the purposes of this subregistry, the BFCP attributes
   for which IANA registration is requested MUST be defined by a
   standards-track RFC.  Such RFC MUST specify the attribute's type,
   name, format, and semantics.

   For each BFCP attribute, the IANA registers its type, its name, and
   the reference to the RFC where the attribute is defined.  The
   following table contains the initial values of this subregistry.

              +------+---------------------+------------+
              | Type | Attribute           | Reference  |
              +------+---------------------+------------+
              |   0  | FLOOR-ID            | [RFC XXXX] |
              |   1  | USER-ID             | [RFC XXXX] |
              |   2  | BENEFICIARY-ID      | [RFC XXXX] |
              |   3  | TRANSACTION-ID      | [RFC XXXX] |
              |   4  | FLOOR-REQUEST-ID    | [RFC XXXX] |
              |   5  | HUMAN-READABLE-INFO | [RFC XXXX] |
              |   6  | DIGEST              | [RFC XXXX] |
              |   7  | REQUEST-STATUS      | [RFC XXXX] |
              |   8  | ERROR-CODE          | [RFC XXXX] |
              |   9  | USER-DISPLAY-NAME   | [RFC XXXX] |
              |  10  | USER-URI            | [RFC XXXX] |
              |  11  | PRIORITY            | [RFC XXXX] |
              |  12  | NONCE               | [RFC XXXX] |
              |  13  | SUPPORTED-TLVS      | [RFC XXXX] |
              +------+---------------------+------------+

       Table 5: Initial values of the BFCP Attribute subregistry


15.2  Primitive Subregistry

   This Section establishes the Primitive subregistry under the BFCP
   Parameters registry.  As per the terminology in RFC 2434 [5], the
   registration policy for BFCP primitives shall be "Specification



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   Required".  For the purposes of this subregistry, the BFCP primitives
   for which IANA registration is requested MUST be defined by a
   standards-track RFC.  Such RFC MUST specify the primitive's value,
   name, format, and semantics.

   For each BFCP primitive, the IANA registers its value, its name, and
   the reference to the RFC where the primitive is defined.  The
   following table contains the initial values of this subregistry.

            +-------+------------------------+------------+
            | Value | Primitive              | Reference  |
            +-------+------------------------+------------+
            |   0   | FloorRequest           | [RFC XXXX] |
            |   1   | FloorRelease           | [RFC XXXX] |
            |   2   | FloorRequestInfoWanted | [RFC XXXX] |
            |   3   | FloorRequestInfo       | [RFC XXXX] |
            |   4   | FloorInfoWanted        | [RFC XXXX] |
            |   5   | FloorInfo              | [RFC XXXX] |
            |   6   | ChairAction            | [RFC XXXX] |
            |   7   | ChairActionAck         | [RFC XXXX] |
            |   8   | Hello                  | [RFC XXXX] |
            |   9   | HelloAck               | [RFC XXXX] |
            |   10  | Error                  | [RFC XXXX] |
            +-------+------------------------+------------+

       Table 6: Initial values of the BFCP primitive subregistry


15.3  Request Status Subregistry

   This Section establishes the Request Status subregistry under the
   BFCP Parameters registry.  As per the terminology in RFC 2434 [5],
   the registration policy for BFCP request status shall be
   "Specification Required".  For the purposes of this subregistry, the
   BFCP request status for which IANA registration is requested MUST be
   defined by a standards-track RFC.  Such RFC MUST specify the value
   and the semantics of the request status.

   For each BFCP request status, the IANA registers its value, its
   meaning, and the reference to the RFC where the request status is
   defined.  The following table contains the initial values of this
   subregistry.









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                   +-------+-----------+------------+
                   | Value | Status    | Reference  |
                   +-------+-----------+------------+
                   |   0   | Pending   | [RFC XXXX] |
                   |   1   | Accepted  | [RFC XXXX] |
                   |   2   | Granted   | [RFC XXXX] |
                   |   3   | Denied    | [RFC XXXX] |
                   |   4   | Cancelled | [RFC XXXX] |
                   |   5   | Released  | [RFC XXXX] |
                   |   6   | Revoked   | [RFC XXXX] |
                   +-------+-----------+------------+

       Table 7: Initial values of the Request Status subregistry


15.4  Error Code Subregistry

   This Section establishes the Error Code subregistry under the BFCP
   Parameters registry.  As per the terminology in RFC 2434 [5], the
   registration policy for BFCP error codes shall be "Specification
   Required".  For the purposes of this subregistry, the BFCP error
   codes for which IANA registration is requested MUST be defined by a
   standards-track RFC.  Such RFC MUST specify the value and the
   semantics of the error code, and any Error Specific Details that
   apply to it.

   For each BFCP primitive, the IANA registers its value, its meaning,
   and the reference to the RFC where the primitive is defined.  The
   following table contains the initial values of this subregistry.






















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   +----------------------+----------------------+---------------------+
   |         Value        | Meaning              | Reference           |
   +----------------------+----------------------+---------------------+
   |           0          | Conference does not  | [RFC XXXX]          |
   |                      | Exist                |                     |
   |           1          | Authentication       | [RFC XXXX]          |
   |                      | Failed               |                     |
   |           2          | Unknown Mandatory    | [RFC XXXX]          |
   |                      | TLV                  |                     |
   |           3          | Floor Request ID     | [RFC XXXX]          |
   |                      | Does Not Exist       |                     |
   |           4          | Unauthorized         | [RFC XXXX]          |
   |                      | Operation            |                     |
   |           5          | User does not Exist  | [RFC XXXX]          |
   |           6          | Invalid Nonce        | [RFC XXXX]          |
   |           7          | DIGEST TLV Required  | [RFC XXXX]          |
   |           8          | Invalid Floor ID     | [RFC XXXX]          |
   |           9          | You have Already     | [RFC XXXX]          |
   |                      | Reached the Maximum  |                     |
   |                      | Number of Ongoing    |                     |
   |                      | Floor Requests for   |                     |
   |                      | this Floor           |                     |
   +----------------------+----------------------+---------------------+

         Table 8: Initial Values of the Error Code subregistry


16.  Acknowledgments

   The XCON WG chairs, Adam Roach and Alan Johnston, provided useful
   ideas for this document.  Additionally, Xiaotao Wu, Paul Kyzivat,
   Jonathan Rosenberg, and Miguel A.  Garcia-Martin provided useful
   comments.

17.  References

17.1  Normative References

   [1]  Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: Keyed-Hashing
        for Message Authentication", RFC 2104, February 1997.

   [2]  Bradner, S., "Key words for use in RFCs to Indicate Requirement
        Levels", BCP 14, RFC 2119, March 1997.

   [3]  Crocker, D. and P. Overell, "Augmented BNF for Syntax
        Specifications: ABNF", RFC 2234, November 1997.

   [4]  Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC



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        2246, January 1999.

   [5]  Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA
        Considerations Section in RFCs", BCP 26, RFC 2434, October 1998.

   [6]  Chown, P., "Advanced Encryption Standard (AES) Ciphersuites for
        Transport Layer Security (TLS)", RFC 3268, June 2002.

   [7]  Yergeau, F., "UTF-8, a transformation format of ISO 10646", STD
        63, RFC 3629, November 2003.

17.2  Informational References

   [8]   Handley, M. and V. Jacobson, "SDP: Session Description
         Protocol", RFC 2327, April 1998.

   [9]   Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
         Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
         Session Initiation Protocol", RFC 3261, June 2002.

   [10]  Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model with
         Session Description Protocol (SDP)", RFC 3264, June 2002.

   [11]  Schulzrinne, H., "Requirements for Floor Control Protocol",
         draft-ietf-xcon-floor-control-req-02 (work in progress),
         October 2004.

   [12]  Rosenberg, J., "A Framework for Conferencing with the Session
         Initiation Protocol",
         draft-ietf-sipping-conferencing-framework-03 (work in
         progress), October 2004.

   [13]  Barnes, M. and C. Boulton, "A Framework for Centralized
         Conferencing", draft-barnes-xcon-framework-00 (work in
         progress), October 2004.

   [14]  Camarillo, G., "Session Description Protocol (SDP) Format for
         Binary Floor Control Protocol (BFCP) Streams",
         draft-camarillo-mmusic-sdp-bfcp-00 (work in progress), April
         2005.











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Authors' Addresses

   Gonzalo Camarillo
   Ericsson
   Hirsalantie 11
   Jorvas  02420
   Finland

   EMail: Gonzalo.Camarillo@ericsson.com


   Joerg Ott
   Universitaet Bremen
   MZH 5180
   Bibliothekstr. 1
   Bremen  D-28359
   Germany

   EMail: jo@tzi.org


   Keith Drage
   Lucent Technologies
   Windmill Hill Business Park
   Swindon
   Wiltshire  SN5 6PP
   UK

   EMail: drage@lucent.com






















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